Recent investigation of optic nerve regeneration in lower vertebrates such as goldfish has found that optic fibers regenerate to many areas that do not normally receive retinal innervation (e.g., ipsilateral optic tectum, inappropriate lamina of the contralateral optic tectum, cerebellum, medulla and pituitary gland). All of these anomalous projections appear to be transient since they can be detected with radioautography only in early, but not in later stages of regeneration. The proposed research, using cobalt-lysine to identify retinal axons, is designed to determine which of these unusual projections are actually, anomalous, since some of them may be present in normal animals. Other studies are directed towards determining whether some of the unusual projections are actually transient. Their disappearance may be a consequence of their retracting or degenerating. Alternatively, radioautography may not be sufficiently sensitive to detect their presence after they stop growing. Studies using retinal ablations will determine whether the occurrence of anomalous projections is related to the increased number of axonal branches that are evident in regenerating optic nerves. Temporal disparities between optic nerve crushes will determine whether the transience of the anomalous projects is related to an unavailability of termination sites. Combined tectal and retinal ablations will be used to determine whether the density of fibers comprising an anomalous projection determines its transience of permanence. The planned research is designed to use a relatively new neuroanatomical method for determining the retinal projections of both normal and regenerating animals. It is anticipated it will reveal novel projections and will thereby contribute to a better understanding of connections within the central nervous system. Clarification of the retinal projections during regeneration may provide insights concerning the mechanisms governing the regeneration process.